The invention relates to a compliant support for an axial thrust air bearing.
Air bearings or foil bearings have been used in high speed turbo machinery, motors, turbochargers, or fluid processing machines which take advantage of their inherent advantages with a flow of compressed air used as a lubricant and coolant. Oil lubricated bearings impose a much higher cost and maintenance load as well as reliability problems associated with oil leakage, filtering and conduits.
However, compared to small scale machines, a gas turbine engine produces relatively high thrust loads on the bearings requiring larger bearings with a higher load capacity. The conducting of air through the bearings creates a compressed air cushion or air film which lifts the bearing surfaces apart to minimize friction.
For example, U.S. Pat. No. 6,286,303 discloses air foil bearings for a gas turbine engine including radial air foil bearings and axial thrust air foil bearings. To date however the permissible tolerance for relatively large diameter air foil bearings, especially axial thrust bearings is less than optimum regarding misalignment, parallelism, squareness and waviness of the running surface as well as load capacity and damping capacity during engine surges.
It is an object of the present invention to provide a simple compliant support for increased load capacity and load damping for axial thrust bearings.
It is a further object of the invention to provide compliant supports for axial thrust bearings that provide an increased manufacturing and operating tolerance for misalignment, parallelism, squareness and/or waviness of the running surface as well as increasing load and damping capacity for the axial thrust air foil bearings.
Further objects of the invention will be apparent from review of the disclosure, drawings and description of the invention below.
A complaint support for an axial thrust air bearing between a haft and a housing with an annular thrust runner extending radially from the shaft having a runner bearing surface. The housing has a housing bearing surface and an air inlet in communication with a source of pressurized air. An annular foil support sleeve is disposed on the housing bearing surface, having an air foil surface with an array of foils. The foils serve to conduct air from the air inlet forming a pressurized air curtain between the runner bearing surface and foils on the sleeve and is then disposed of through an air outlet. The sleeve has a complaint surface with at least one compliant annular ring. The compliant surface includes at least one compliant annular ring such as a fluorocarbon O-ring for low temperature service under 300xc2x0 F.; a fluorosilicon O-ring for mid-range temperature service 300-600xc2x0 F.; or a metallic mesh ring for high temperature service over 600xc2x0 F.